(1) Field of the Invention
The present invention relates to an optical disk drive, and more particularly to an optical head moving section of an optical disk drive.
(2) Description of the Related Art
In a conventional optical disk drive, a moving section is constituted by an optical head or a part of the optical head, and a guide structure therefor is constituted by a plurality of rolling members provided to the moving section and a pair of rails fixed on a base of the disk drive. The plurality of rolling members are in a rolling contact with the pair of rails under pressure, whereby the moving section is maintained in a state in which, due to the above guide structure, the moving section is allowed to move along a surface of a disk medium.
FIG. 1 diagrammatically shows a side view of a relevant portion of such conventional optical disk drive which has as a guide structure six rolling members 1a-1f each having a cylindrical outer surface and a pair of rails 2a, 2b. As seen in FIG. 1, in order to maintain the moving section 3 in the required position, one of the rolling members 1a-1f, that is, the rolling member 1b is held by the moving section 3 through a spring member such as a plate-spring 4 which urges the rolling member 1b to a certain fixed direction. FIG. 1 shows that the rolling member 1b is inclined by 45 degrees and pressed against the rail 2a by the spring 4 which is fixed to the moving section 3 and whose spring force urges the rolling member 1b against the rail 2a. The rolling member 1b together with the rail 2a restricts the movement of the moving section 3 to the left along the X-axis shown in FIG. 1 and also restricts the upward movement thereof along the Z-axis. The rolling members 1e and 1f are fixed to the moving section 3 with 45 degree inclination, and they together with the rail 2b restrict the movement of the moving section 3 to the right on the X-axis and also restrict the upward movement thereof along the Z-axis. The rolling members 1a, 1c and 1d vertically in contact with the rails 2a and 2b restrict the downward movement of the moving section 3. Hence, the moving section 3 is allowed to move freely along only the Y-axis (shown in FIG. 2B). In the conventional disk drive using such rolling members, at least six of them are required in order to be able to maintain a stable operating posture of the disk drive.
The problems in the conventional optical disk drive described above include the following. To realize the pressing means utilizing a spring as explained above, the structure becomes complex with the disk drive becoming large and costly. Also, although the rolling members having cylindrical outer surfaces are less costly by themselves, the number of the rolling members required is large with the minimum number being six and this makes the overall cost high. Furthermore, the complexity of the structure inevitably involves a larger number of manufacturing steps resulting in lower precision and higher manufacturing cost.